This invention relates to engine ignition analyzers, i.e., engine tune-up equipment, and in particular to a new and improved strobe or timing lamp.
A standard accessory for use with the conventional engine analyzer is the strobe or timing lamp which provides a pulse of light of very short duration. In a typical internal combustion engine, a fixed reference mark is provided on the engine housing adjacent the flywheel which carries another reference mark. When these two reference marks are aligned, the engine is in the top dead center position which normally corresponds to the firing time for the number 1 cylinder.
The conventional strobe lamp is triggered by the number 1 cylinder firing signal during running of the engine producing the repeating short light pulse permitting visual determination by the mechanic of the actual engine flywheel position with respect to the fixed reference mark for any engine speed. Originally, the mechanic noted the difference between the two reference marks, typically in degrees scribed on the flywheel, to determine the amount of advance of number 1 cylinder firing signal with respect to top dead center. In improved timing lamps, a variable delay was introduced into the timing lamp so that the lamp trigger pulse was delayed with respect to the number 1 cylinder firing signal. In using this improved lamp, the mechanic adjusted the delay so that the two reference marks were aligned when the lamp was triggered and read the calibration of the delay adjustment in terms of degrees of advance.
This type of device generated a voltage proportional to engine speed which voltage was used as a reference for the delay circuit. This simple delay circuit has been satisfactory for prior engines which were set at some amount of advance.
The present day engines, particularly those equipped with pollution control devices, incorporate both advance and retard mechanisms, and some engines are set at a retarded position at idling speed. The simple time delay circuits utilized with the prior art strobe lamps cannot be used for measuring retard settings, that is, the lamps cannot be utilized to advance the lamp firing ahead of the cylinder firing signal. Accordingly, it is an object of the present invention to provide a new and improved method and apparatus for controlling the firing of a strobe lamp.
It is a particular object of the invention to provide a new and improved control method and apparatus for an engine strobe lamp suitable for measuring both advance and retard engine timing. A further object is to provide such a device which is suitable for use with engines of various numbers of cylinders, and one which can be utilized to provide lamp firing at the zero degree position as well as advance and retard positions.